Machine-switching telephone-exchange system.



C. L. GOODRUM.

MACHINE SWITCHING TELEPHONE EXCHANGE SYSTEM. APPLICATION r1150 SEPT.16, 1915.

Patented Feb. 1, 1916.

mfnasseax THE COLUMBIA FLAPjOORAPH co., WASHINGTON, D. c.

CHARLES L. GOODRUM, OF NEW YORK, N. Y., ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, CORPORATION OF NEW YORK.

Specification of Letters Patent.

' Patented lFeb. 1, rain.

Application filed September 16, 1915. Serial No. 50,987.

To all whom it may concern:

Be it known that I, CHARLES LANE Goon- RUM, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Machine Switching Telephone Exchange Systems, of which the following is a full, clear, concise, and eXact description.

This invention relates to telephone exchange systems, and more particularly to such systems wherein calling lines are associated with connecting circuits by means of line finders. In such systems the removal of the receiver by the calling party closes the circuit of the primary stepping magnet of the finder, which, by interrupting its own circuit, drives the finder brushes in a primary direction to select the group of terminals containing the calling line. When the calling group is reached and the finder brushes properly positioned, the circuit of the secondary stepping magnet of the finder is closed, which by interrupting its own circuit, drives the brushes over the terminals of the calling group in search of the calling line therein. It may happen that the line finder, having been started in motion, fails to connect with the calling group or the calling line. Thus, the calling line is not extended to a connecting circuit, and, moreover, if a starter wire is employed for associating the finders with the lines, the remaining lines will be without service, due to the disabling of the starter wire circuit ordinarily extended by the finder side switch as the finder arrives upon the calling line terminals.

It is the object of this invention to restore the finder if it fails to function properly and allow it again to hunt for the calling line, and the novelty consists in the provision of a circuit arrangement whereby if the armature of either of the stepping magnets rests on its back contact for a predetermined length of time, a circuit is closed for the release magnet ofthe finder, whereby the finder is restored. In the arrangement shown, the winding of the release magnetis placed in series with a resistance and the circuit leads through the armatures and back contacts of the primary and sec-- ondary stepping magnets. Thus, if the release magnet circuit is closed through this resistance, and the armature and back contact of either of the magnets fora predetermmed interval of time, the release magnet becomes energized and releases the finder, whereby it may again begin its hunting movement.

The invention will be more readily understood when described with reference to the accompanying drawing which shows only so much of a system as is necessary for a comprehension of this invention.

The subscribers lines are divided into groups and terminate in multiple terminals 32, 33 of finder switches, the number depending on the trafiic. Each line is provided in the finder with a test terminal 34. The removal of the receiver by a calling party energizes the line relay 10, which by operating the relay 1 1 common to the group to which the calling line belongs, closes the circuit of the primary stepping magnet 22 of the finder. The brush shaft 40 of the finder carries a set of brushes 29, 30, 31 for each group of lines to which it has access. The finder then in a primary movement positions the proper set below multiples of the calling line group. The changeover operation then occurs to switch the secondary stepping magnet 23 into circuit to cause such set of brushes to wipe over the multiples 32, 33, 3 1, thereof. The test brush 31 is grounded during this operation and successively energizes the cut-off relays 11 of the lines of the calling group.

. minals.

The invention will be best understood by describing the operations involved in tracing a call; The removal of the receiver by the calling party at substation A' energizes line relay 10 over the following circuit: free pole of battery, left winding of relay 10, left armature and back contact of cut-off relay 11, conductor 12, over the line circuit and through the telephonic apparatus at substation A, conductor 13, right-hand armature and back contact of relay 11 to ground through the right winding of relay 10. Relay 10 locks itself in series with a relay 14.- common to this group of lines, over the following circuit: free pole of battery, left winding of relay 10, left armature and back contact of relay 11, left armature and spring of relay 10, conductors 16, 17, left armature and back contact of relay 18 to ground through the relay 14. Relay 14 thereupon g which this finder has access.

looks itself to conductor 16 in a circuit independent of the armature and back contact of relay 18, and at its right armature and front contact closes a circuit to energize a slow relay 19. The attraction of this armature also grounds a terminal 20 of a group switch G, which group switch is carried by the finder, the brush 28 thereof rotating with the brush shaft 40 and being adapted to wipe over the terminals t of the line groups to Relay 19 at its left armature and front contact, energizes relay 18, which, by attracting its right armature, interposes a break in the release circuit. Assuming that the finder apportioned to the line group to which the calling substation A belongs is idle, the following circuit is closed, upon the energization of the group relay 14 and slow relay 19, to energize the side switch escapement magnet 27 to release the side switch into the second position to initiate the secondary movement of the line finder, since no primary movement of such finder is necessary, it being understood that the line finder apportioned to a line group, if idle, hasa set of brushes 29, 30, 31 in operative relation to multiples 32,33, 34 'of such group. The circuit to operate magnet 27 is as follows: free pole of battery, right armature and back contact of magnet 21, primary magnet 22, conductor 26, side switch magnet 27 side switch arm 3, brush 28 of switch G, contact 20, right armature and front contact of relay 14 to ground. The primary magnet, while included in this circuit, is not energized, due to its low resistance relative to that of magnet 27. The escapement magnet, however, is immediately energized and allows the side switch to escape into the second position in the well-known manner.

In position 2 the escapement magnet 27 is maintained energized over the following circuit: free pole of battery, armature and back contact of magnet 21, magnet 22, conductor 26, magnet 27 arm 3 and its second contact, conductors 24, 25, right armature and front contact of relay 19, right armature and front contacts of relays 19 and 14 to ground. In position 2 of the side switch, the following circuit is closed'to drive brushes 29, 30, 31

of the line finder over the multiples 32, 33 and 34 of the calling line group: free pole of battery, armature and back contact of release magnet 21, secondary stepping magnet 23, arm 1 and its second contact, conductor 41, armature and back contact of magnet 23, conductor 42, armature and front contact of magnet 27 conductors 24, 25, armatures and front contact ofrelays 19 and 14 to ground. The stepping magnet 23 makes and breaks its own circuit, thus driving the brushes 29, 30, 31 over the multiples 32, 33, 34. In position 2 of the side switch, the arm 4 connects ground to the test brush 31 of the line finder over the following circuit: ground, right armature and front contact of relay 14, right armature and front contact of relay 19, conductor 25, arm 4 and its second contact to test brush 31. The cut-off relays 11 of the lines of the calling group are energized in succession as the brush 31 engages the multiples 34 of such lines. When the terminal 34 of the calling substation is reached, the energization of its cut-off relay 11 opens the circuit traced for the group relay 14. This relay, in retracting its right armature, removes ground from the circuit traced for the secondary stepping magnet 23, thus stopping the finder upon the calling line terminals, and also removes ground from the circuit traced for escapement magnet 27, which releases the side switch into position 3. The calling line is now extended over brushes 29, 30 and side switch arms 5, 6 either to a first selector or to an operators position (not shown). Arm 1 extends starter wire over conductor (36 to the next idle finder.

In position 1 of the side switch, in parallel with the circuit traced through the primary stepping magnet 22, a circuit is closed for the release magnet 21 as follows:. free pole of battery, magnet 21, resistance 35, side switch arm 2 and its first contact, side switch arm 1, armature and back contact of magnet 23, armature and back contact of magnet 22, conductor 24, conductor 25 to ground, through the armatures and front contacts of relays 19 and 14. The resistance of release magnet 21 and the resistance 35 are so proportioned that the magnet 21 will not pull up its armatures by the impulses it receives through the armature and back contact of magnet 22, these impulses being of too short duration to sufiiciently energize said magnet. However, if for any reason the primary movement of the finder does not progress in the normal manner, and the armature of magnet 22 remains on its back contact longer than a predetermined interval, the release magnet becomes energized and restores the finder and side switch to normal. By attracting its left armature, it looks itself over the following circuit: free pole of battery, magnet 21, left armature and front contact of said magnet, ofi'-normal contact 36 to ground at the first selector (not shown). This off-normal contact opens when the finder completely restores and deenergizes the release magnet. If the primary movement of the finder takes place properly, but the succeeding secondary movement of the switch is not successfully accomplished and the armature of secondary stepping magnet 23 rests on its back contact for a relatively long interval, the

1,169,800 lit following circuit is closed for the release magnet 21 in position 2 of the side switch: free pole of battery, magnet 21, resistance 35, side switch arm 2 and its second contact, side switch arm 1 and its second contact, armature and back contact of magnet 23, armature and front contact of magnet 27 to ground through the armatures and front contacts of relays 19 and 14:. The release magnet thereupon restores the finder and side switch and locks itself in the circuit previously traced, which is opened when the off-normal spring 36 is restored.

What is claimed is:

1. In a telephone exchange system, the combination with telephone lines, an automatic finder switch to which said lines are multipled, a stepping magnet adapted to drive said finder, a circuit for said stepping magnet including its armature and back contact, and a release magnet for said finder, of a circuit including said release magnet and leading through the armature and back contact of said stepping magnet and adapt ed if closed for a predetermined length of time to release the finder.

2. In a telephone exchange system, the

combination with telephone lines, an automatic finder switch to which said lines are multipled, a stepping magnet for driving said line finder, and a release magnet for said finder, of a circuit for said release magnet including the armature and back contact of said stepping magnet, a resistance in said circuit, said circuit being adapted when closed for a predetermined interval to energize the release magnet.

8. In a telephone exchange system, the combination with a plurality of lines, an automatic finder switch wherein said lines terminate in groups, primary and secondary stepping magnets for said finder, a release magnet for said finder, of a circuit including said release magnet leading through the armatures and back contacts of said stepping magnets, a resistance in said circuit, said circuit being adapted when closed for a predetermined interval to cause said release magnet to attract its armatures to release the finder.

In witness whereof I hereunto subscribe my name this 11th day of September A. D.,

CHARLES L. GOODRUM.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. C. 

